Laboratory Evaluations of Synthetic and Natural Insecticides on Beet Armyworm (Lepidoptera: Noctuidae) Damage and Survival on Lettuce

Abstract

Laboratory studies were conducted to test the effects of synthetic and natural insecticides on lettuce leaf consumption by beet armyworm, Spondoptera exigua (Hübner). Two synthetic and 4 natural insecticides we compared: Capture (bifenthrin), Lannate (metnomyl), Success (spinosad), Xentari (Bacillus thuringiensis subsp. aizawai), Kryocide (cryolite), and Trilogy (90% neem oil extract). Capture, Lannate, Success, and Xentari at 50 ppm (AI) caused 100% mortality within 1 d after exposure and prevented any detectable feeding on eat disks by neonate S. exigua larvae. Capture, Lannate, Success, and Xentari at 50 ppm allowed only minor feeding by 3rd and 5th instar S. exigua before causing nearly 100% mortality. Xentari at 50 ppm appeared less effective than the synthetic insecticides and Success, but statistical differences among them were not significant. Neither Kryocide nor Trilogy at 50 ppm reduced leaf consumption by neonate, 3rd instar, and 5th instar S. exigua compared with controls Higher concentrations of Kryocide and Trilogy (1,000 and 10,000 ppm) did significantly reduce leaf consumption by 3rd instar S. exigua. The most effective natural insecticides we tested for reducing lettuce consumption by S. exigua were Success and Xentari.